Detergent manufacturers have long recognised the need to control water hardness to ensure adequate cleaning by detergents. The detergency builders used in the past for this purpose have been of three main types, namely water-soluble sequestering builders, water-insoluble ion exchange builders and water-soluble precipitating builders. A typical precipitating builder is an alkali metal carbonate, especially sodium carbonate. Other water-soluble precipitating builders include sodium silicate (particularly effective against magnesium hardness), sodium orthophosphate and water-soluble alkali metal soaps.
The calcium ion concentration in a wash liquor can be reduced to sufficiently low levels by the use of, for example, a sequestering builder material such as sodium tripolyphosphate, and for this reason, considerable commercial success has been achieved with phosphate-built formulations. However, it has now become apparent that, under some conditions, the discharge of significant quantities of phosphates into waste waters may produce environmental problems. There is therefore an increasing desire in some countries to reduce the level of phosphorus in detergent compositions.
It has previously been thought that it was essential for precipitating builders to be substantially soluble at the temperature of use to achieve efficient water softening. With the present trend towards washing fabrics at lower temperatures with a view to saving energy costs, it has not previously been thought possible to use, as a precipitating builder material, materials which themselves are not substantially soluble in water at low temperatures. Thus, fatty acid salts which are not substantially soluble in water at room temperature, have not previously been proposed for use as precipitating builder materials at low wash temperatures.
We have now surprisingly found that certain fatty acid salts, which are not substantially soluble in cold water, can be incorporated together with a selected detergent active compound and a special carrier material into a solid particle, which can exhibit rapid dissolution or dispersion in, and efficient building of calcium-hard water, even at low temperatures. These built detergent particles can be used with or without other detergent active components and detergent adjuncts for use in the washing of fabrics.